Liquid conductor heater



June 24, 1941. M, W HANKS 2,246,677

LIQUID CONDUCTOR HEATER Filed Feb. 16, 1938 2 Sheets-Sheet l @77E-Wfl@ @Wam-m Filed Feb. 16, 1938 2 Sheets-Sheet 2 umn Patented June 24, 1941 LIQUID CONDUCTOR HEATER Marshall W. Hanks, Madison, lWis., assignor to Hankscraft Company, Madison, Wis., a corporation of Wisconsin Application February 16, 1938, Serial No. 190,816

(ci. 21e-4o) heated liquid to the supply conductors which are 7 Claims.

This invention relates to improvements in liquidlconductor heaters of the type disclosed, for example, in the United States Patent No. 1,683,071, granted to Marshall W. Hanks and Max Mason on September 4, 1928, in which a pair of spaced electrodes connectedin an electric circuit are located in a vessel of insulating material and adapted to be connected by a measured quantity ot water or other vaporizable liquid which is adapted to be heated, and evaporated to substantial dryness, by the passage of current therethrough, thus giving the apparatus a substantially definite time period of operation.l By

suitably regulating the measured quantity of' liquid which is put into the vessel, the duration of the operation oi' the apparatus may be varied as desired. 'Ihe apparatus of the present invention may be used i'or warming a babys milk bottle, or for cooking eggs, or for heating or cooking various other objects for definite time periods which are automatically terminated bythe evaporation of the liquid, without attention on the part oi' the operator, but the invention is disclosed herein as being applied to a milk bottle warmer. of the type described and claimed in my copending application Serial No. 156,159, illed July 28, 1937.

In the construction and use of liquidv conductor heaters of the type referred to it is common practice to connect the spaced electrodes to the terminals of an electric circuit by a ilexible electric cord comprising a pair of conductors twisted together andY having their extremities connected to the electrodes beneath the vessel. It has been found that the heat developed in the apparatus, by the passage of current between the electrodes causes a rise'in thev temperature of the conductors of the electric cord considerably above that produced by the normal passage of electric current therethrough with the result that such apparatus has in some instances been regarded as a nre hazard and it has been difficult to obtain its approval under all circumstances by ilre insurance underwriters, and the like.

The principal object oi' the present invention is to overcome the above mentioned diiiiculty by providing an improved liquid conductor heater oi' the type referred to comprising means for preventing the undue rise in temperature of the supply conductors. A further object is to provide a liquid conductor comprising a vessel of insulating material provided with a cavity or well which serves as a trap to prevent the conduction of heat from the electrodes and the withaportio'riofthe bottom cover connected to the electrodes. Still another object of the invention is to provide a liquid conductor heater comprising improved means for interlocking the supply conductors with parts of the insulating vessel in which the spaced electrodes are located, to relieve strain upon the connections between the conductors and the electrodes, in combination with means for preventing the abnormal rise of temperature of the conductors adjacent to the point or points where they are interlocked with the vessel. Other objects relate to various features of construction'and arrangement which will appear more `fully hereinafter.

The nature of the invention will be understood from the following specification taken with the accompanying drawings in which one embodiment is illustrated. In the drawings,

Figure 1 shows a perspective view of' one form of the improved liquid conductor heater of the present invention, which is shown as being used for heating a babys milk bottle:

. Fig. 2 shows an enlarged top plan View of the liquid conductor heater shown in Fig. l'with the milk bottle removed;

Fig. 3 shows a vertical section taken on the line 3 3 of Fig. 2;

Fig.- 4 shows a vertical section taken on the line 4-4 of Fig. 2

Fig. 5 shows a horizontal section taken on the line 5 5 of Fig. 3;

Fig. 6' shows an enlarged top plan view of the nutvor washer which is engaged by a bolt by which the insulating plate is held above the electrodes;

Fig. 'I shows an enlarged bottom plan view of the electric conductcnheatershownmin Pig. 1 q plate or name plate removed;

Fig. 8 shows a side elevation of the insulating plate which is mounted over the electrodes:

Fig. 9 shows a bottom plan view of the insulating plate shown in Fig. 8;

Fig. 10 is an enlarged vertical sectional view taken on the line l-il of Fig. '1, showing the well or cavity which prevents the transfer of heat from the .interior of the vessel to the supply conductors; and

Fig. 1l shows an enlarged vertical section of the line Il-II of Fig. 7, illustrating the means for connecting the terminals of the electrodes with the supply conductors.

As illustrated in the drawings, the invention comprises a vessel I5 formed of porcelain or other suitable insulating material, which is adapted to receive the article or object to be heated or cooked. In this instance, a babys milk bottle I6 is shown mounted in the cavity of the vessel. The vessel l has an outer annular wall lil, a bottom wall lh, and a lower annular flange or base portion i5 adapted to rest upon a table or other support and forming a bottom cavity ld in which connections are established with a pair of spaced electrodes ll and I8 which are located in the bottom of the vessel, resting on the bottom wall ISD. 'I'he electrodes il and I8 are preferably formed as bare round wires of conducting material which are wound in spiral fashion and located one within the other so that convolutions of one electrode are located on oppositie sides of each convolution of the other electrode. The convolutions of the separate electrodes are maintained in place laterally on the bottom wall l5 and are spaced from adjacent convolutions of the other electrode by means of projections l5 which are formed integrally with the bottom wall i5 and which project upwardly therefrom. These projections 95 are preferably arranged in rows extending radially outward from the center of the vessel as shown in Fig. 5.

The electrodes l'l and la are heldin place on the bottom wall IED by means of an insulating plate 2li formed of porcelain or other suitable insulating material which rests upon the upper edges of the electrodes and which is secured in place by a bolt 2i engaging a nut 22 which is located in a recess l5f formed in the upper suriace of the bottom wall i5. The nut 22 is preferably in the form of a fiat spring washer as shown in Fig. 6, being notched on one side as shown at 228. This washer is of a diameter slightly greater than the diameter of the upper part oi the circular recess if in the bottom wall oi the vessel, and the central aperture 522 in this washer is of a diameter such that it fits the bottoms of the spaces between the threads of the bolt, so vthat the washer forms a onethread nut. When this washer is pushed downwardly into the recess lbf, it assumes a down= wardly convexed shape and is retained in the recess by the engagement with the wall thereof and the extremity of the bolt 2l may be threaded into engagement therewith to hold the insulating plate 2d in tight engagement with the electrodes ll and l so that these electrodes are clamped against the bottom wall of the vessel.

The insulating cover plate 2li is provided on itsupper side with a central annular surface ll and three outwardly radiating surfaces is which are horizontal and which are adapted to be engaged by the bottom of the milk bottle it. The portions oi the insulating plate between the horizontally radiating fiat portions 2d are inclined downwardly as shown at 26, forming radiating troughs Q0". These troughs are inclined downwardly and outwardly so that any or other liquids, as it is desirable that all portions of this liquid reach the electrodes to be heated and vaporized, thus giving the apparatus a definite time period of operation. The head of the bolt 2| is located in a central recess or depression 20 formed in the upper side of the insulating plate and the stem of the bolt extends through a central boss 2l)1 from which three anges or arms 2lig extend radially outward, being united integrally with the under side of the body of the plate. These ilanges or arms 20' are preferably located directly beneath the ilat portions 20 upon which the bottle i 6 rests, and the lower edges of these flanges 20g are adapted to engage the upper edge portions of the electrodes l1 and I8 which are thus clamped between the anges and the bottom wall l5b of the vessel. 'I'he flanges or arms 2l)l thus form the cavities 2lih which are open at their outer ends and which serve as boiling spaces immediately above the electrodes so that there is a free opportunity for bubble formation as the liquid in the vessel is heated and vaporized. The plate 20 is preferably slightly less in diameter than the internal diameter of the lower portion of the cavity of the vessel l5 so that there is an annular space 23 around the outer edge of the plate 29 to permit the upward escape oi bubbles which are produced by the heating of the liquid. In addition, the ready escape of these bubbles is insured by the provision in the body portion of the plate 2d of a number of apertures 201 which are preferably located in the inclined portions 2Ei of the troughs, as shown in Fig. 2.

The electrodes Il and i8 are connected in a supply circuit by having portions llEl and i8* thereof, respectively, led downwardly through apertures i511 which are formed in the bottom wall of the vessel. After inserting these portions oi the electrodes through the apertures l5, the apertures may be sealed by any suitable waterproof cement which is adapted to withstand any heat which may be generated by the passage of current through the electrodes. If desired, portions of rubber tubing may be inserted around the electrodes in the apertures before applying the cement. The extremities of the electrodes are connected to supply conductors 25 and 26 which are surrounded by insulation to form a common exible cord 2 having. at the end thereof a tting 23, as shown in Fig. 1, which permits the connection of the conductors 25 and 2t in an electric circuit. In order to connect the extremities oi the electrodes with the oonductors 25 and 2t, which have the insulation removed from the inner ends thereof, without the use of screws or other usual fastening means, the bottom wall l5 of the Vessel is provided on its underside with a pair of elongated grooves or recesses B51 which have their side walls tapared upwardly. The bare extremities of the conductors 2d and 2S are laid across these grooves and then, after placing the extremities l'lb and lsb of the electrodes transversely across these extremities of the supply conductors, these portions llb and lh of the electrodes are pushed upwardly into the grooves ii, thereby forming U-shaped bends in the extremities of the conductors 25 and 2S, as shown in Fig. ll, and causing these conductors to be held in frictional engagement with the extremities of the electrodes. In order to compensate for various diameters of the wires and electrodes which may be employed with a particular vessel l5, shims 29 of any suitable material may be placed above the conductors 2li and 26 before the parts are pushed into the grooves |51, as shown in Fig. 11, and the shims may be selected of any suitable thickness to cause a tight wedging lit when the parts have been pushed into the grooves. 'I'he conductors 25 and 28 may be prevented from shifting laterally adjacent the grooves Ii by providing bosses |5J on the underside of the bottom wall I5b of the vessel, as shown in Fig. '1, these bosses being located in pairs and spaced apart to receive one of the conductors between them.

For the purpose of locking the insulated portions of the conductors 25 and 25 to prevent any tension created in the cord 21 from being transmitted to the connections which are formed between these conductors and the electrodes, the conductors 25 and 25 'are bent transversely adjacent the aperture |55 through which the supply core 21 is brought in through the base flange I5 of the vessel, and the bottom wall of the vessel is provided with two locking lugs I5l which are iormed integrally with this wall and which extend downwardly at opposite sides of the axis oi' the aperture |55 so that the conductors 25 and 26, in passing around these lugs I5l are compelled to make sharp bends with respect to the cord 21 preliminary to being attached to the electrodes, as shown in Fig. 7. In addition, the two conductors 25 and 25 may be knotted together just inside of the aperture |55, as shown by dotted lines at 21n thus providing an enlargement of larger area than the aperture |55 so that any longitudinal strain on the cord 21 is transmitted by the knot 21 to the base flange I5 of the vessel. Without this knot 215, the angular disposition of the portions of the containers 25 and 26, which are positioned just inside of the aperture |55, will prevent undue strain from being transmitted to the connections between the conductors and the electrodes.

For the purpose of preventing undue heating of the conductors 25 and 25 in the region of the bottom wall of the vessel, the vessel I5 is provided with an upwardly extending cavity or well I5m which is arcuate in cross section, both horizontally and vertically, as illustrated in Figs. 7 and 10, the outer wall of this cavity forming an upward continuation of the inner surface of the base ilange I5c of the vessel and the inner wall ofthe cavity extending concentric with the inner wall of the vessel, thus forming an air space extending horizontally beyond the portions of the conductors 25 and 2l which are passed around the lugs I51 while at the same time extending vertically to a considerable degree above those portions oi' the conductors which pass through the aperture |55 An openlng I5n is preferably provided'leading outwardly to the atmosphere from the upper part of the cavity to permit a free circulation of air through the cavity. This air space serves as a heat insulator to prevent the transfer of heat from the interior of the vessel to the conductors 25 and 25 in the cord 21 where it passes through the aperture |55, thus bringing about a substantial reduction in the temperature of those portions of the conductors 25 and 25 which lie beneath the vessel, and, in particular, of that portion of the cord 21 which lies within the aperturc |55. This reduction in temperature is sutilcientto remove all danger of heating to the point where combustion would take place and has led to the approval of a device of this kind for use under all circumstances.

The connections of the supply conductors with the electrodes are preferably concealed by a cover plate 30, formed of suitable sheet metal or the like, which seats against the annular shoulder I5r formed on the inner portion oi' the base iiange of the vessel. In order that this cover plate may be secured to the vessel without use of screws or other similar fastening means, the base of the vessel is provided with a projecting boss I5o against which the cover plate 2l is adapted to seat and this boss is provided with a downwardly extending stud |51. which may be circular in cross section, and which is preferably provided around its outer surface with a plurality of vertically extending ribs or serrations I5q which are adapted to bite into the wall of a circular aperture 305 formed in the plate 3l. When the plate is driven upwardly over the stud |59. the metal will interlock with the porcelain of the boss |5 and thus hold the plate in place. This cover plate 35 may serve as a name plate` for the manufacturer and also to carry printed directions for the operation of the apparatus.

llAlthough one form of the invention has been shown and described by way of illustration, it will be understood that it may be constructed in various other embodiments coming within the scope of the appended claims.

Iclaim:

1. A liquid conductor heater comprising an insulating vessel adapted to contain a measured quantity of liquid, a pair of spaced electrodes in said vessel adapted to be connected by said liquid, said vessel having a bottom wall with a continuous annular flange extending downwardly therefrom to rest upon a support, said ange having an aperture therethrough communicating with the space beneath said bottom wall, and a pair ,of electric supply conductors leading through said aperture and connected to said electrodes, said insulating vessel having .a cavity therein extending upwardly from the region of said conductors and positioned to limit the transi'er of heat from the interior of said vessel to said conductors in the vicinity of said aperture.

2. A liquid conductor heater comprising a vessel oi insulating material having a chamber adapted to contain a measured quantity of liquid, a pair of spaced electrodes in said chamber adapted to be connected by said liquid, said vessel having a bottom wall and a continuous annular base flange extending downwardly. below said bottom wall to rest upon a support. said ilange having an aperture therethrough communicating with the space beneath said b ottom wall, and a pair of electric supply conductors leading through said aperture and having connections wlth'said electrodes, said vessel having a cavity therein leading upwardly from' said conductors within the upward projection of the area enclosed by said base flange and positioned with its upper part horizontally outward from the lower part of said chamber.

3. A liquid conductor heater comprising a vessel of insulating material having a chamber adapted to contain a measured quantity of liquid, a pair of spaced electrodes in said chamber adapted to be connected by said liquid, and a pair of electric supply conductors having connections with said electrodes, said vessel having a supporting base flange provided with an aperture through which said conductors extend and having a cavity extending upwardly from said conductors inside the said base flange and horizontally outward from said chamber, said vessel having a Ventilating opening leading outwardly to the atmosphere from the upper part of said cavity.

4. A liquid conductor heater comprising a vesof insulating material having a chamber "adaptedto contain a measured quantity of liquid,

a pair of spaced electrodes in said chamber adapted to be connected by said liquid, and a pair oi electric supply conductors having connections with said electrodes, said vessel having an annular supporting base ilange provided with an aperture through which said conductors extend and having a cavity extending upwardly from said conductors inside the area enclosed by the said base flangel and positioned horizontally outward from a part of said chamber, said cavity being arcuate in cross section both horizontally and vertically, said vessel having an opening leading outwardly to the atmosphere from the upper part of said cavity.

5. A liquid conductor heater comprising a vessel of insulating material having a chamber adapted to contain a liquid, a pair of spaced electrodes in said chamber adapted to be connected by said liquid, said vessel having a bottom wall and an annular supporting flange extending downwardly thereirom, said flange having an aperture therein, a pair ot electric supply conductors leading through said aperture and p0- sitioned adjacent said bottom wall, said conducltors and said electrodes having connections through said bottom wall, and insulating posts carried by said bottom wall to spread said conductors apart within said ange. said vessel having a cavity extending upwardly from said conductors in the region between said flange" and said posts to effect the cooling of said conductors.

6. A liquid conductor heater comprising a vessel of insulating material having a chamber adapted to contain a liquid, a pair of spaced electrodes in said chamber adapted to be connected by said liquid, said vessel having a bottom wall and an annular supporting flange extending downwardly therefrom, said ange having an aperture therein, a pair of electric supply conductors leading through said aperture and 4 7. A liquid conductor heater comprising a ves-` sel of insulating material having a chamber adapted to contain a liquid, a pair of spaced electrodes in'said chamber adapted to be connected by said liquid, said vessel having a bottoni wall and an annular supporting ilange extending downwardly therefrom, said ange having an aperture therein, and a pair of electric supply conductors leading through said aperture and positioned adjacent said bottom wall, said conductors and said electrodes having connections Ithrough said bottom wall, said conductors being knotted within said aperture to prevent longitudinal strains thereon from being transmitted to said connections, said vessel having a cavity therein extending upwardly in the wall thereof in the region of said knot to effect the cooling of said conductors.

MARSHALL W. HANKS. 

